Many applications for electronic devices rely on a high reliability and availability of the electronic devices. Modern automotive applications demand safety complaint ICs (integrated circuits) to be used in automotive systems. Accordingly with the actual reference standard ISO 26262, the chip must be identified in an ASIL (Automotive Safety Integrity Level), thus satisfying a set of rules during the safety lifecycle process and implementing a set of safety mechanisms to ensure its reliability in case of fault. The ISO 26262 dictates the procedure to produce ASIL parts, components or entire systems.
High level of safety is requested in angle sensing applications, for example, thus angle sensor ICs must deal, beside technical requirements, with safety requirements and fully satisfy them. If on one hand the ISO development process can assure the compliance to safety, on the other hand the hardware metrics of the chip address it to an ASIL classification. The higher is the classification the safer is the IC, exploiting the open of a broader market and of a set of applications. Reaching the highest metrics is often a challenge due to design factors that impact the metric calculation.
To a higher metric classification a lower number of Failures In Time (FIT) is associated. The FIT is a temporal hardware failure identifier and it is dependent on the area of the chip and on the number of residual faults. The residual faults FITs can be lowered applying safety mechanisms on the chip blocks to secure them. The mechanisms can be both internal to the chip, representing internal features that reveal faulty blocks, or external to the chip, in the form of external measures.
To achieve a high ASIL level, the Single-Point Fault Metric (SPFM) as well as the Latent Fault Metric (LFM) have to reach high values (e.g. >95%), for example. The achievement of a high SPFM depends on mechanisms executed during operation. On the other hand, the LFM is strongly linked to safety mechanisms which are carried out at the startup of the IC (start-up BISTs, start-up built-in self-test).